I have the same bug and i've been searching around many topics regarding this post as to compare with my own experience with this bug. as alex says this is VERY GROUNDBREAKING!!!
I have played 240 days on my savegame and i was to help Lethwin-Far-Seeker to reclaim his throne. the bug first appeared when i convinced a lord to join my cause, he just happened to own a castle and a village. it was now my color (red) each 10 seconds this "talk window" pops up with sometimes only bank written on it, but i noticed that if you talk to somebody, it repeats the last said word to me instead of being blank. as i said this is VERY GROUNDBREAKING and you CANNOT play while this bug appears. This bug is a MUST to repair within the next patch, if not i'll have to wait several weeks before i again can continue my campaign. here are some of the examples of the text: "blank - Continue..." "Indeed, please continue - Continue..." "You'll have to speak to me some other time then - Continue" as i said, it repeats the last said word if you talked to somebody. but still pops up each 10 seconds and MUST be fixed VERY shortly
P.S
Bought the game via steam. EAGERLY WAITING FOR THIS TO GET FIXED!!